Field of the Invention
The invention relates to a communication system including at least two private branch exchanges each having a call controller and at least one switching node connected to at least one higher-level communication network through a network interface unit and connected to terminals through at least one subscriber line module, one of the private branch exchanges having a team function controller controlling certain terminals as team terminals of a team, to be called through the switching node of that private branch exchange, in accordance with a team function and, in doing so, initiating signaling to other team terminals and influencing their call-processing state in dependence on a call-processing state of individual team terminals.
Such interconnected private branch exchanges, in at least one of which a team function is implemented, are known, among others, in the form of the HICOM 300 private branch exchange commercially sold by Siemens AG. A known team function is, for example, the "call acceptance" function in which incoming calls are indicated in a call acceptance group of a number of terminals and can be answered at any terminal which belongs to the call acceptance group. Another known team function is the "line group" function which can be reached under a social collective number. In that configuration, any subscriber of a line group can also be called directly through an individual call number. However, the special collective number reaches all subscribers. The collective number is allocated, for example, to a master terminal.
A further known team function is the integrated secretarial unit, which is also called a manager/secretary station.
In known communication systems, all subscribers of a team are connected to a single private branch exchange and are switched to a higher-level communication network through the same network interface unit.